Determination of tellurium in indium phosphide by electrothermal atomic absorption spectrometry and ultraviolet–visible spectrophotometry

Abstract

Two electrothermal atomic absorption spectrometry (ETAAS) methods have been developed for the determination of tellurium in indium phosphide doped with cadmium telluride. Samples are dissolved in concentrated hydrochloric acid and nitric acid (3 + 1) and analysed by ETAAS. For samples containing more than 5 µg g^–1 Te, the diluted solution is injected into the furnace with a Pd^II–Mg^II chemical modifier. Matrix-matched standards are necessary. The detection limit (3s) is 0.8 µg g^–1 for a 200 mg sample. When the tellurium content is less than 5 µg g^–1, the digest is evaporated to dryness, the residue is dissolved in 3 mol dm^–3 hydrochloric acid and tellurium is extracted into chloroform containing Bismuthiol II. By injecting the organic phase into the furnace, a detection limit (3s) of 0.3 µg g^–1 is achieved for a 500 mg sample. In order to control the accuracy of the first ETAAS procedure, a UV-VIS spectrophotometric method using Bismuthiol I, formerly proposed for palladium, was extended to the determination of tellurium in indium phosphide. The molar absorbivity of the Te–Bismuthiol I complex at 447 nm is 20.8 × 10⁴± 4.3 × 10³ dm^–3 mol^–1 cm^–1(95% confidence). The detection limit (3s) obtained by the UV-VIS method is 6.5 µg g^–1 for a 250 mg sample. Comparative results obtained by different methods on real samples are presented.